Is human life really so cheap that ownership of guns outweighs it?

Another mass killing of innocent children in America. With the right to own/bear arms, why are there so many people who happily take their weapons to gun down children? Why are there not rules about carrying weapons in public?

In Switzerland, there are rifles in every home, since all Swiss are members of the national militia. But you never hear of mass killings. Same in Austria. In the United States, there must be some widespread psychological problem that young people think they can fulfil some delusion by killing innocent children.